Process of isolating betaine from guayule extract



Patented Apr. 24, 1951 PROCESS OFISOLATING BETAINE FROM GUAYULE EXTRACTThomas F. Banigan, Jr., and James W. Mocks,

Salinas, Calif., and Ralph W. Planck, New 0rleans, La., assignors to theUnited States of America as represented by the Secretary of AgricultureN0 Drawing. Application January 17, 1950, Serial No. 139,111

'7 Claims. (Cl. 260-501) Granted under the act of March 3, 1883, as

amended April 30, 1928;

Methods are known for isolating betaine from i natural sources but thesemethods give low yields and/or involve cumbersome techniques. One knownmethod involves acidifying an aqueous extract of guayule withhydrochloric acid then concentrating the acidified-extract, filteringolf precipitated material and allowing the betaine hydrochloride tocrystallize out of solution. Thisand similar methods which are based onisolation of betaine as its hydrochloride give poor yields particularlybecause of the high solubility of the betaine hydrochloride, i. e., 59parts per 100 parts water.

1 It has now been found that betaine can be isolated in high yields fromits source materials by a simple procedure. In essence our processinvolve 'crystallizing the betaine as its phosphate from a solution ofthe source material in an 'alcohol or other oxygenated organic solvent.

Thus in proceeding in accordance with thisinvention, a solution of thesource material in an oxygenated organic solvent is first prepared. Thissolution is then acidified with phosphoric acid and the betainephosphate allowed to crystallize out of solution. The efliciency of ourprocess stems essentially from the fact that betaine phosphate has asolubility in alcohol of only one-eighth that of betaine hydrochloridein this solvent. Thus we have determined that in 95% ethanol at 25 C.,the solubility of the phosphate is 0.28% whereas the solubility of thehydro-,- chloride is 2.16%. It is to be emphasized that it could not bepredicted that the phosphate would be so poorly soluble in alcoholbecause in water the reverse situation exists, i. e., the phosphate hasa solubility of 72.98 parts per 100 parts water and the hydrochloridehas a solubility of 59.43 parts per 100 parts water. Another advantageof our process over the method using hydrochloric acid i that thestarting solution need not be concentrated to the high degree to inducecrystallization and high yield of product as required with thehydrochloride process. Eliminating the necessity for drasticconcentration, which usually involves heat, tends to preserve theidentity and the nature of the other components in the solution many ofwhich are thermally unstable. Another point is that in our process, thephosphoric acid need not be added in great excess. Usually little morethan a stoichiometric quantity of phosphoric acid is required to obtainquantitative precipitation of the desired salt in contrast to the twotothreefold excess of hydrochloric acid required to induce crystallizationin the known process. This factor is important in that the mother liquorremaining from our process is still useful for isolation of othercomponents. Thus We can use the mother liquor from our process for therecovery of parthenyl cinnamate by the process set forth in the patentapplication of J. W. Meeks, T. F. Banigan, Jr., and R. W. Planck, SerialNo. 127,564, filed November 15, 1949. Other advantages of our processare that the crystals of betaine phosphate attain a desirable size morerapidly and are more free of colored contaminants than in thehydrochloride process.

In preparing the oxygenated organic solvent solution of thebetaine-containing source material one can proceed in many alternativeways. One method is to extract the source material with water,concentrate the aqueous extract by evaporation, decolorize it ifnecessary by treating it with active carbon or other decolorizing agent,filter off insoluble material and mix the concentrate with theoxygenated organic solvent.

Another method is to extract the source material with an oxygenatedorganic solvent thus to prepare directly the desired solution. Inisolating betaine from guayule it is most convenient to start with thesolution which is obtained when comminuted guayule shrub or resinousguayule rubber is extracted with an oxygenated organic solvent for thepurpose of removing the resin from such materials as an incident topreparing resin-free guayule rubber. This solution is preferably treatedto remove the resin prior to the betaine isolation step. Thus thesolution so obtained is evaporated preferably under vacuum to causeseparation of the solution into two phasesa non-resinous phasecontaining the betaine and a resin phase. The non-resinous phase canalso be referred to as a water extract or aqueous phase as it containswater and water-soluble constituents derived from the guayule material.The non-resinous phase is separated from the resin phase and dissolvedin an oxygenated organic solvent and concentrated if necessary.Preferably, this solution is de-waxed before carrying out the isolationprocedure. This dewaxing can be accomplished readily by allowing thesolution to stand, preferably under-refrigeration, whereupon the waxwill precipitate out of solution and can easily be separated as byfiltration or centrifugation. However, it is not essential to removewaxes at this point as the betaine phosphate precipitating out in thesubsequent treatment has such low solubility in the oxygenated solventcompared to the waxes that purification of the crude precipitate may bereadily effected by solvent washings and/or recrystallization. Theconcentration of betaine in the solution of the source material is notcritical because of the low solubility of betaine phosphate. In general,we prefer to use solutions which contain 20% or less of betaine as suchsolutions yield crystalline betaine phosphate of high purity and largecrystal size.

A wide choice is possible with regard to the particuiar oxygenatedorganic solvent used. In

general, we prefer to use those solvents which are useful for thederesination of guayule shrub or resinous guayule rubber. Thus ethanolis preferred because of its low cost, high solvency characteristics forguayule resin, and particularly because of its relatively poor solvencypower with regard to the betaine phosphate. Other solvents which may beused are, for example, methanol, propanol, isopropanol, butanols,acetone, and so forth. If desired, mixtures of individual solvents maybe employed.

Having prepared a solution of the source material in the oxygenatedorganic solvent, the solution is then treated with phosphoric acid toform the betaine-phosphoric acid salt. Generally, we

employ the commercially available 85% phosphoric acid. The amount ofacid used should be such as to provide equimolar proportions of HsPOiand betaine, however, we generally add a slight excess (about 1( %25%)of the acid to ensure rapid crystallization of the betaine phos- Vphate. The betaine phosphate crystals are separated as by dccantation,filtration, or centrifuga tion and may be further purified by washingwith the oxygenated organic solvent, by dissolving in a minimum quantitof water and reprecipitating by the addition of oxygenated organicsolvent or by recrystallizing from the oxygenated organic solvent. Thepoint at which the phosphoric acid is added is not critical. Thus thesource material may be first acidified with phosphoric acid and thenmixed with the oxygenated organic solvent.

The betaine phosphate isolated by our procedure and purified bydissolving in a minimum of water and precipitation with ethanol isobtained as large, white platelet crystals with a melting point of210-21l C. and has the formula If desired, betaine phosphate may beconverted by appropriate chemical treatment into other useful compounds.Thus by simple metathesis the phosphate can be converted into othersalts such as the hydrochloride, picrate, sulphate, and so forth.Further, the phosphate may be .converted into betaine itself by wellknown procedures such as by ion exchange.

The following example demonstrates the process of this invention ingreater detail. It is understood that this example is submitted only byway of illustration and not limitation.

EXAMPLE (A) Preparation of alcohol extract 125 gallons of an acetoneextract of comminuted guayule shrub (variety 593) containing 1.5% solidswas subjected to evaporation under vacuum. The residue separated into 2phases--an upper non-resinous (aqueous) phase (1.5 gallons) and a'lowerphase consisting of the guayule resin (1.35 gallons). The non-resinousphase was mixed thoroughly with 5 gallons of 95% ethanol and allowed tostand. After several hours the clear supernatant solution was decantedfrom the dark residue of waxes (about 350 grams, dry weight) andconcentrated under vacuum to an aqueous alcoholic solution weighing 8kilograms and containing 63% solids.

(B) Crystallization of betaine phosphate To a 100-gram aliquot portionof the aqueous alcohol solution prepared in part A was added 10 grams of85% phosphoric acid. Immediately, the betaine phosphate crystallized outof solution in the form of small prisims which were separated bydecanting. Yield: 13.6 grams of betaine phosphate.

The mother liquid was evaporated to dryness and the residue was found tocontain no betaine nor betaine phosphate. Thus it was determined thatthe process resulted in quantitative crystallization of the betainephosphate.

(C) Crystallization of betaine hydrochloride The following experiment isnot illustrative of the process of this invention but is furnished todemonstrate the poor results obtained when using the hydrochloridemethod.

An attempt was made to isolate betaine as its hydrochloride by addinghydrochloric acid to an aliquot portion of the aqueous alcohol solutionprepared in part A. It was found that approximately three times themolar quantity of hydrochloric acid was used as compared to thephosphoric acid used in part B before crystallization was observed tobegin. The crystals formed slowly over several hours and were obtainedas very small monoclinic prisims and fragments.

The betaine recovery was much less than with the use of phosphoric acid.

Having thus described our invention, we claim:

1. The process of isolating betaine as its phosphate from the solventextract obtained in the preparation of resin-free guayule rubber whichcomprises concentrating the extract, allowing the concentrated extractto separate into a non-resinous phase containing betaine and a resinphase, separating the non-resinous phase, mixing it with an oxygenatedorganic solvent and acidifying it with phosphoric acid, then separatingthe betaine phosphate which crystallizes out of solution.

The process in accordance with claim 1 wherein the oxygenated organicsolvent is ethanol.

.3. The process in accordance with claim 1 wherein the oxygenatedorganic solvent is acetone.

4. The process of isolating betaine in the form of its phosphate fromguayule which comprises evaporating an oxygenated organic solventextract .of guayule, allowing the evaporated extract to separate 'into anon-resinous phase containing betaine and a resin phase, separating thenonresinous phase, mixing it with an oxygenated organic solvent,acidifying the resulting solution with phosphoric acid and separatingthe betaine phosphate which crystallizes out of solution.

5. The process of isolating betaine as its phosphate from thenon-resinous phase which is 5 formed when an oxygenated organic solventextract of guayule is concentrated which comprises mixing saidnon-resinous phase with an oxygenated organic solvent, acidifying theresulting solution with phosphoric acid and separating the 10 betainephosphate which crystallizes out of solution.

6. The process of isolating betaine as its phosphate from thenon-resinous phase which is formed when an oxygenated organic solventex- 15 tract of guayule is concentrated which comprises mixing saidnon-resinous phase with an oxygenated organic solvent, dewaxing theresulting solution, acidifying the dewaxed solution with phosphoric acidand separating the betaine phos- 20 phate which crystallizes out ofsolution.

7. The process of isolating betaine as its phosphate from thenon-resinous phase which is formed when an oxygenated organic solventextract of guayule is concentrated which comprises mixing saidnon-resinous phase with about 3 volumes of ethanol, allowing thesolution to stand until the waxes are precipitated, separating thewaxes, acidifying the de-Waxed solution with phosphoric acid and.separating the betaine phosphate which crystallizes out of solution.

RALPH W. PLANCK. THOMAS F. BANIGAN, JR. JAMES W. MEEKS.

REFERENCES CITED The following references are of record in the file ofthis patent:

Andrlik, Chem. Zentr., vol. 1904, II, 309-310.

Andrlik, Chem. Zentia, vol. 1915, 11;265-266.

1. THE PROCESS OF ISOLATING BETAINE AS ITS PHOSPHATE FROM THE SOLVENTEXTRACT OBTAINED IN THE PREPARATION OF RESIN-FREE GUAYULE RUBBER WHICHCOMPRISES CONCENTRATION THE EXTRACT, ALLOWING THE CONCENTRATED EXTRACTTO SEPARATE INTO A NON-RESINOUS PHASE CONTAINING BETAINE AND A RESINPHASE, SEPARATING THE NON-RESINOUS PHASE, MIXING IT WITH AN OXYGENATEDORGANIC SOLVENT AND ACIDIFYING IT WITH PHOSPHORIC ACID, THEN SEPARATINGTHE BETAINE PHOSPHATE WHICH CRYSTALLIZES OUT OF SOLUTION.